In the present study, the prevalence of PTAs on CT angiography was 0.6% and mostly left-sided (57%). Most PTA cases are often asymptomatic and PTAs are found incidentally on angiographic imaging performed for other reasons.
As per literature, depending on the procedures employed (such as CT angiography, MRI angiography, and DSA) PTAs have an estimated prevalance of approximately 0.1–1%. . The prevalence of PTAs were reported as 0.54, 0.33, 0.51, and 0.63 by Chen et al. , Weon et al. , Uchino et al. , and Bai et al. , respectively in studies conducted using MR angiography. Kalmykov et al.  found the incidence rate as 0.58 in a study conducted using CT angiography. The reported incidence rates ranged from 0.2 to 0.37 in studies performed assessments using conventional, CT, as well as MR angiographies [9, 15]. In the present study, only CT angiography images were investigated, and the prevalence of PTAs was found to be consistent with the results reported by the majority of the relevant studies. Some studies reported that the prevalence of a right-sided PTA was higher than that of a left-sided PTA [9,15-,16], whereas others suggested the opposite . In the present study, a left-sided PTA was more prevalent than a right-sided PTA, and there was no bilateral PTA case.
In the literature, PTAs have been more frequently observed in females than in males. However, no statistically significant difference was found in terms of sex [9, 18]. Although the majority of the patients (70%) with PTAs in our study were female, there was no significant correlation between the prevalence of PTAs and sex, consistent with the literature.
PTAs are associated with a variety of pathologies, including vascular nerve compression syndromes, such as trigeminal neuralgia and ophthalmoplegia, caused by oculomotor nerve involvement or abducens palsy. PTAs were also suggested to be associated with hypopituitarism owing to a spontaneous or traumatic intracavernous fistula and brain aneurysms . PTA rupture and bleeding during surgical or interventional procedures is often fatal. Accordingly, the extension, localization, and classification of PTAs and accompanying vascular pathologies significantly influence potential surgical or interventional procedures. In addition, the relationship of PTAs with the abducens nerve should be clarified as PTA may present with different clinical manifestations . In a study that examined 4,650 patients who underwent brain MR angiography and classified patients with PTAs based on Saltzman classification, the prevalence of each type was as follows: type I, 24%; type II, 16%; and type III, 60% . In the present study, type I was the most prevalent type and types II and III were found at a similar rate. Similar to other studies in the literature, lateral/petrosal-type predominance was found in terms of the relationship of the PTAs with the abducens nerve [9, 10, 12, 14, 15].
The prevalence of intracranial vascular anomalies increases in the presence of PTAs . Proximal basilar artery hypoplasia is the most prevalent vascular anomaly and occurs in 65–75% of PTA cases. Accordingly, it is an auxiliary marker in addition to the radiological detection of PTA [11–15]. Although the most prevalent comorbid vascular pathology in the present study was basilar artery hypoplasia, it was found at a lower prevalence (42%) compared to that reported in the literature.
Certain studies have reported that the prevalance of aneurysms increases to 14% in the presence of PTA owing to the hemodynamic forces arising from the presence of persistent artery and congenital disorders of the medial layers of the cerebral vesselsMost aneurysms occur at the level of the vascular junction and originate at the circle of Willis. Aneurysms of the PTA are exceptionally rare [7, 11, 14, 17]. In the present study, there was no significant aneurysm originating at the circle of Willis. A fusiform aneurysm was found at the PTA junction in 1 case (14%); this prevalence is higher than that reported in the literature. This might have been attributable to the relatively small number of PTA cases in the present study
In addition, diffuse wall calcification at the PTA level was observed in 1 case. PTA case with this feature has not been found in the literature.
It has been reported that the presence of PTA may also be associated with ischemic stroke [18–20]. In patients with PTA and vertebrobasilar hypoplasia, the vascular supply to the posterior fossa may tend to decrease. Relevant literature suggests that there may be a relationship of transient ischemic attack and vertigo, which is considered as the first symptom of transient ischemic attack, with PTA [21–26]. In the present study, one patient had a chronic ischemic infarct in the right half of the bulb. This patient had left-sided Saltzman type I and Salas medial type PTA along with basilar artery hypoplasia.
PTAs can originate from different segments of the ICA. Arra'ez-Aybar et al. reported that most of the PTAs originated from the posterior wall of the cavernous segment of the ICA (C4) and a small number of PTAs originated from the petrous segment . The C4 segment is often reported as the origin of PTAs [9, 17–21]. Most of the PTA cases in the present study (85%) originated from the posterior wall of the cavernous segment (C4) of the ICA, and few (15%) originated from the petrous part. These findings are consistent with studies in the literature.
Our study had some limitations. It was designed as a retrospective study and reflected the results of a single-center study with a comparatively small number of patients. Further prospective and multicenter studies are warranted.